5 CFR § 550.706 - Criteria for meeting the requirement for involuntary separation.
(a) An employee who resigns because he or she expects to be involuntarily separated is considered to have been involuntarily separated if the employee resigns after receiving -
(1) Specific written notice that he or she will be involuntarily separated by a particular action effective on a particular date; or
(2) A general written notice of reduction in force or transfer of functions which -
(i) Is issued by a properly authorized agency official;
(ii) Announces that the agency has decided to abolish, or transfer to another commuting area, all positions in the competitive area (as defined in § 351.402 of this chapter) by a particular date (no more than 1 year after the date of the notice); and
(b) Except for resignations under the conditions described in paragraph (a) of this section, all resignations are voluntary separations and do not carry entitlement to severance pay.
(c) A resignation is not considered an involuntary separation if the specific or general written notice is canceled before the separation (based on that resignation) takes effect.